Here is if everyone want to know the updates:
Fixed a bug where Ursena’s and Mitsuko’s reflecting status effects were not blocking negative effects such as mana reduction.
Here is complete update notes V25.
If it is by design only for Ursena and Mitsuko, then it should written in skill with word: including mana reduction, otherwise others heroes must be also apply like Grazul, Gato, Aeron, etc. Just like OP said.